Method and apparatus for operating polyphase dc motors

• US 5,306,988 A
• Filed: 10/03/1991
• Issued: 04/26/1994
• Est. Priority Date: 10/03/1991
• Status: Expired due to Term

• Current Assignee: SGS-Thomson Microelectronics (STMicroelectronics NV)
• Original Assignee: SGS-Thomson Microelectronics (STMicroelectronics NV)
• Inventors: Carobolante, Francesco, Rohrbaugh, Mark E.
• Primary Examiner(s): Roskoski, Bernard
• Assistant Examiner(s): MARTIN, DAVID S
• Application Number:
  US07/770,577
• Time in Patent Office: 936 Days
• Field of Search: 318/254, 318/138, 318/439
• US Class Current: 318/400.34
• CPC Class Codes: H02P 6/00 Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor vector control H02P21/00
• CPC Class Codes: H02P 6/085 in a bridge configuration
• CPC Class Codes: H02P 6/182 using back-emf in windings
• CPC Class Codes: H02P 6/32 Arrangements for controlling wound field motors, e.g. motors with exciter coils

Abstract

A circuit for operating a polyphase dc motor, for example of the type having a plurality of "Y" connected stator coils, has circuitry for unambiguously determining the actual instantaneous position of the rotor of the motor, circuitry for determining a desired rotor position precedent to executing a desired commutation sequence, and circuitry for executing the desired commutation sequence when the circuit for determining the actual instantaneous position of the rotor detects that the rotor is actually in the desired rotor position. The circuitry for unambiguously determining the actual instantaneous position of the rotor includes a back emf amplifier switchably connected to at least one floating coil, and circuitry for determining when the voltage received by the back emf amplifier crosses a reference voltage from a predetermined direction. In one embodiment, the circuit, includes mask circuitry for inhibiting the reference voltage crossing detection circuitry for a predetermined time after a change in the commutation sequence. The mask circuitry includes clocked up and first and second down counters, the second down counter being inhibited to be clocked until the first down counter has reached a predetermined count, and the reference voltage crossing circuitry being inhibited until at least the second down counter has completed its count. When a reference voltage crossing is detected, the count of the up counter is loaded into both the first and second down counters, then the up counter is reset to begin a new commutation period count.

Claims